Shares of General Motors Co. fell to a 10-month low Friday as the company’s widening recall crisis put a coveted upgrade of its credit rating in doubt.

Standard & Poor’s said Thursday that it might put off a potential upgrade of GM’s debt to investment grade status until next year. S&P issued a statement after the automaker boosted the estimated costs of its recently announced recalls to $1.3 billion.

GM stock hit $32.51 in morning trading, a low since June, before recovering to $32.70 at midday. June was also the last time the stock dropped below GM’s $33 initial public offering price.

The stock has dropped almost 6 percent since Feb. 13, when GM began a series of recalls, including 2.6 million small cars for a deadly ignition switch problem.